1. Field of the Invention
The present invention relates to antioxidant compositions and, more particularly, to antioxidant compositions for use in stabilizing host materials containing organic materials.
2. Description of the Prior Art
As noted in U.S. Pat. Nos. 3,330,859; 3,285,855; 4,228,297; 5,696,281; 5,739,341; and 5,821,206, to mention a few, stcrically hindered phenols are known stabilizers for host materials--i.e., organic materials or compositions containing organic materials--that are susceptible to thermal, oxidative, and/or actinic degradation. In particular, virtually all polymers, be they synthetic or natural in origin, react with oxygen, such oxidation reactions normally occurring while the polymer is being thermally processed at elevated temperatures. Depending upon the polymer, the oxidation/degradation can manifest itself as discoloration, loss of gloss or transparency, cracked surfaces, loss of mechanical properties such as tensile strength and elongation, etc. In addition to polymers, numerous other host materials such as lubricants, polyols, fuel oils, surfactants, and personal care products--e.g. lotions, creams, etc.--are susceptible to oxidation/degradation, which can affect their appearance and/or effectiveness for their intended usage.
While there are other methods of reducing degradation/oxidation of organic materials or compositions containing organic materials, by far the most common means of achieving this result is by the use of antioxidants, particularly sterically hindered phenols. Hindered phenols exhibiting antioxidant properties can be either liquid or solid in nature, liquid antioxidants possessing the advantage that they are easier to meter into the host material. Regardless of whether the hindered phenols are liquid or solid, thermal stability, resistance to coloration, and purity are important physical properties. Additionally, in the case of liquid antioxidants, physical properties such as liquidity at high molecular weight, low viscosity at low temperatures, low pour points, low volatility, and low freeze points are also important considerations. In particular, the problem that exists to the present time in the antioxidant technology area is the lack of high molecular weight liquid antioxidants that are of high purity, have low freezing points near or below 0.degree. C.--e.g., less than about 5.degree. C. and can be identified/analyzed at low concentrations in the host material. In the latter regard, it will be recognized by those skilled in the art that antioxidants, be they liquid or solid, are typically used at levels below 5,000 ppm. Being used at such low levels, it is important that the level of antioxidant in the host material be easily analyzed so as to ensure that the proper amount of antioxidant is present. By way of example, antioxidants are important polymer additives. If the appropriate amount of antioxidant is not added to polymeric compositions, deleterious effects in the polymer can occur. Such deleterious effects include discoloration, accelerated aging, thermal degradation during production, loss of physical properties, etc.
It therefore would clearly be desirable to have antioxidant compositions that, at low levels, could be accurately analyzed in the host material. It would be especially desirable to have liquid antioxidant compositions that exhibit high purity, low freezing or pour points, and low viscosity at low temperatures.